SelectedValue which is invalid because it does not exist in the list of items

I encounter this problem repeatedly, and haven't a clue what is causing it. I get an exception in the DataBind: SelectedValue which is invalid because it does not exist in the list of items.

Here are some important pieces of information:

1. I reload listOrgs periodically when the underlying data has changed.
   
2. The Organization.DTListAll call returns 2 Int, String pairs.
3. There are no duplicate or null values in the returned data
4. After the first two lines below, listOrgs.Items.Count is 0, and the Selected Value is 0
5. The selected value after the DataBind operation executes is the ID value from the first row in the data
6. This exception happens the very first time this code is executed after a fresh page load

listOrgs.Items.Clear(); 
listOrgs.SelectedValue = "0"; 
listOrgs.DataSource = new Organization().DTListAll(SiteID); 
listOrgs.DataTextField = "OrganizationName"; 
listOrgs.DataValueField = "OrganizationID"; 
listOrgs.DataBind();